They don't exactly 'throw up' but they produce digestive juices on to the food. This predigests it so they can suck it up. Keep your food covered!
By spitting juices on the food, then slurping the mixture up.
Control the houseflies and take care that they the food is covered so that they do not sit on the food and make it contaminated. you can use anti- houseflies solutions which stop the houseflies entering your home.
Yes, this is the way a fly has to eat.
Houseflies are quite useful to the environment as they help in decomposing of substances. They are also used as food by certain animals on earth.
No, it you throw up the food, it does not matter if it is healthy or not. You eat anything and then throw it up to lose weight. But do not do it, it can lead to serious health issues later in life.
Too be honest it is best not to throw up at all but you would need to vomit all of the food back up (do not recommend this) but remember food is compacted when you chew and swallow so a small amount of vomit could be a size-able meal
because your body needs food to be able to function so its not going to throw it up it needs the protein
There are no houseflies in Alaska.
Mabey to much food
Yes, they can carry all sorts of serious diseases. Which they distribute on your food.
No food should make you throw up. If you do throw up from food after eating it, that is probably because you ate too much, ate too fast, the food was bad (spolied, rotten, left out too long, undercooked, overcooked, ect.), or you had some sort of reaction - possibly and allergic reaction - to it.
Houseflies are born from maggots.